Water pressure actuated electric switch for cable cutter

ABSTRACT

A sealed hollow capsule having inner and outer ends and a side wall contains a pair of electric contacts spaced lengthwise of the capsule, the outer end of which supports one of the contacts. The side wall has an annular groove in it reducing the thickness at that point to a thin band that is compressible to reduce its width when a predetermined pressure is exerted against the outer end of the capsule so that one contact will engage the other contact. The switch is especially suitable for closing an electric circuit connected with electrical firing means in an explosively actuated cable cutter.

lJnited States Patent 1191 1111 3,739,673 Temple 5] June 19, 1973 [541WATER PRESSURE ACTUATED ELECTRIC 2,920,532 l/l960 McBride 114 221 A xSWITCH FOR CABLE CUTTER 211 App]. No.: 217,116

US. Cl. 83/639, 83/925 R, ll4/22l A Int. Cl..' B26d 5/12 Field of Search83/639, l, 925 R;

[56] References Cited UNITED STATES PATENTS 5/l972 Burke 83/639 X l/l950Austin 2/1972 Rosenthal 83/639 Primary Examiner-Andrew R. JuhaszAssistant Examiner-James F. Coan AttorneyBrown, Murray, Flick & Peckham[57] ABSTRACT A sealed hollow capsule having inner and outer ends and aside wall contains a pair of electric contacts spaced lengthwise of thecapsule, the outer end of which supports one of the contacts. The sidewall has an annular groove in it reducing the thickness at that point toa thin band that is compressible to reduce its width when apredetermined pressure is exerted against the outer end of the capsuleso that one contact will engage the other contact. The switch isespecially suitable for closing an electric circuit connected withelectrical firing means in an explosively actuated cable cutter.

5 Claims, 4 Drawing Figures 1 WATER PRESSURE ACTUATED ELECTRIC SWITCHFOR CABLE CUTTER There are situations in which a ship is being towed orheld in position by another ship, where it is desirable to cut the towcable immediately upon the occurrence of a nearby underwater explosion.If this is not done, the force of the explosion may cause the ships toput such tension on the cable as to cause it to break and snap backtoward the ships, where it may cause damage or injury. In othersituations it is desirable to lower an object through deep water bymeans of a cable, and to release the cable from the object after it hasreached the desired depth so that the cable can be recovered. This hasbeen difficult to do heretofore.

It is among the objects of this invention to provide an electric switchwhich is closed by water pressure, which can operate a cable cutter,which will be closed by surge pressure caused by an underwaterexplosion, or which can be calibrated to close at a specified waterdepth if allowed to sink through the water. Another object is to providea cable cutter controlled by such a switch.

The preferred embodiment of the invention is illustrated in theaccompanying drawings, in which FIG. 1 is a side view of the cablecutter and switch hanging from a cable;

FIG. 2 is a fragmentary enlarged vertical section taken on the lineII-II of FIG. l;

FIG. 3 is an enlarged vertical section of the switch; and

FIG. 4 is a similar view showing the switch closed.

Referring to FIG. 3 of the drawings, a pair of electric switch contacts1 and 2 are rigidly mounted inside of a sealed capsule 3 having innerand outer ends connected by a side wall. The inner contact 2 may besupported by the capsule in any suitable manner, such as by aninsulating plug 4 sealed in an axial opening in the inner end of thecapsule. The other contact is supported by the outer end of the capsulea predetermined distance from the inner contact. To allow this distanceor gap to be adjusted, the outer end of the capsule includes a screw 5that supports the outer contact. By turning t'hat screw, the gap can beadjusted. The side wall of the capsule is provided with an annulargroove ti that reduces the thickness of the wall in that area to a thinband that is easily deformed in a manner to be described presently.

The capsule 3 is mounted in an axial socket in the outer end of a metalhousing 11. The inner end of the capsule is encircled by a sealing ring12. From the inner end of the socket a short passage 13 extends into anaxial bore 14 in the inner end of the housing. This bore contains aninsulating ring 16 engaged by a rubber flange 17 on the end of anelectric cord 18. In this flange the inner contact 2 is connected withone of the wires 19 in the cord. The other wire 20 is soldered to asplit metal ring 21 encircling the cord between flange l7 and a secondrubber flange 22. The ring engages the encircling housing and is pressedtightly against it by the portion of the cord inside the ring. Thatportion expands when the two rubber flanges are clamped tightly betweeninsulating ring 16 and a flanged bushing 23 that is held in place by anut 24 screwed onto the inner end of the housing. The outer contact 1 iselectrically connected through the metal capsule 3 and housing 11 withthe metal ring 21 and wire 20.

When this switch is submerged in water and the water pressure againstthe outer end of the capsule becomes great enough, the water will movethe outer end of the capsule inwardly to cause the thin metal band ofits side wall to compress, as shown in FIG. 4. The band compresses bybending radially inward or outward upon itself. When this occurs, theouter contact 1 moves into engagement with the inner contact 2 to closethe switch. In order to increase the effective area against which thewater pressure acts, a cup-like pressure cap 26 is slidably mounted onthe outer or lower end of housing 11 around the capsule. The end wall ofthe cap is spaced from the end of the housing, preferably by having thecapsule project from the housing, or in an equivalent manner byproviding the cap with a central projection small enough to enter thehousing socket 10. The cap is held against the capsule by means ofcircumferentially spaced headed pins 27 screwed into the cap andslidably mounted in holes through a flange 28 encircling the housing andspaced from the inner or upper end of the cap. Water is prevented fromentering the space between the outer end of the housing and the cap by asealing ring 29 mounted in a groove, such as in the periphery of thehousing. It will be seen that water pressure against the outer end faceof the cap sufficient to overcome the resistance of the thin band in thecapsule wall will push the outer end of the capsule inwardly, causingthe thin band to collapse and thereby allowing the two contacts toengage each other.

Although the electric switch disclosed herein can be used for variouspurposes, it is especially suitable for firing an explosively actuatedcable cutter, as shown in FIGS. 1 and 2. Such a cutter may include aframe 30 provided with a barrel in which a chisel 31 is slidablymounted. The frame has a recess 32 in one side to permit a cable 33 toenter it between the chisel and an anvil 34 in the front end of theframe. The frame can be locked onto the cable by means of a retractablesleeve 36 slidably mounted on the frame and urged forward across theentrance to recess 32 by a coil spring 37 that engages a cartridgeholder 38 screwed into the rear end of the frame behind the chisel. Anexplosive charge or cartridge 39 is disposed in the holder and containsa hot wire primer 40. This primer is connected by a wire 42 with acontact 43 on the back of an insulating member 44 disposed in the rearend of the cartridge holder. The contact engages a battery 45 in thefront end of a tube 46 that is clamped against the rear end of thecartridge holder by means of a threaded collar 47. The tube is filledwith enough batteries to provide the desired voltage. The primer is alsoconnected by a wire 48 to a split metal ring 49 that tightly engages thesurrounding wall of the cartridge holder.

At the opposite end of tube 46 one of the batteries engages a contact 51that is electrically-connected by a wire 52 to a filter 53 screwed intoa grounding ring 54. The lower end of the filter is in electricalcontact with a pin 55 that projects into a socket 56 on the end of wire19 in the electric cord. This end of the cord is formed like the otherend and is held in a coupling 57 screwed onto the rear end of thebattery tube. The other wire 20 of the cord is electrically connectedwith the coupling through a split metal ring 58 between two rubberflanges 59 and 60 on the cord. A flanged bushing 62, held in place by anut 63 screwed onto the lower end of coupling 57, presses against flange60.

To provide for severing a tow cable between two ships, the cutter can behung on the cable with the electric switch hanging down into the wateras shown in FIG. 1. The cord 18 is long enough to allow the switch to besubmerged a considerable distance, such as fifty feet for example. Anunderwater explosion that causes a surge pressure great enough to movehousing 11 and cap 26 toward each other will close the switch contacts 1and 2 and thereby fire the cutter. This will cause the chisel 31 tosever the cable 33.

Instead of being used for the purpose just described, the cutter may beattached to a cable that is to lower an object to the ocean bed, whereit is to be left. In order to be able to retrieve the cable, the cutteris attached to it close to the object being lowered and the switch isset to operate at the water pressure existing near the ocean bed. Whenthe switch reaches that depth, the water pressure is great enough tocollapse the thin wall portion of capsule 3 and thereby close the switchcontacts to fire the cutter. A short cord 18 would generally be used sothat the switch would be close to battery tube 46. Also, instead of thecable cutter being provided with its own batteries, a battery locatedabove the water could be used by connecting it by means of a longelectric cord to the pressureactuated switch, which would beelectrically connected with the electric primer 40.

According to the provisions of the patent statutes, I have explained theprinciple of my invention and have illustrated and described what I nowconsider to represent its best embodiment. However, I desire to have itunderstood that, within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically illustrated anddescribed.

I claim:

1. A water pressure actuated electric switch comprising a sealed hollowcapsule having inner and outer ends and a side wall, a pair of electriccontacts in the capsule spaced lengthwise thereof, one of the contactsbeing supported by the outer end of the capsule, said side wall havingan annular groove therein reducing the thickness of a portion of theside wall to form a thin band in the wall, and said band beingcompressible to reduce its width when a predetermined pressure toexerted against said outer end of the capsule, whereby to permit saidone contact to engage the other contact, wires electrically connectedwith said contacts and adapted to be electrically connected with asource of electricity, and an electrically fired cable cutter in serieswith one of the wires.

2. A cable cutter comprising a cutting member, an explosive charge foractuating said member, electrical firing means for said charge, anormally open electric circuit containing said firing means, and anormally open water pressure actuated switch in said circuit for closingit when the switch is exposed to a predetermined water pressure.

3. A cable cutter according to claim 2, including a frame for saidcutting member and explosive charge and firing means, said circuitincluding batteries, and a sealed housing for the batteries rigidlyconnected to the frame.

4. A cable cutter according to claim 2, in which said switch includes asealed hollow capsule having inner and outer ends and a side wall, apair of electric contacts in the capsule spaced lengthwise thereof, oneof the contacts being supported by the outer end of the capsule, saidside wall having an annular groove therein reducing the thickness of aportion of the side wall to form a thin band in the wall, and said bandbeing compressible to reduce its width when a predetermined pressure isexerted against said outer end of the capsule, whereby to permit saidone contact to engage the other contact.

5. A cable cutter according to claim 4, including a housing containingsaid capsule with the outer end of the capsule projecting from thehousing, and a cup-like pressure cap engaging said outer end andslidably mounted on said housing in sealing engagement therewith.

1. A water pressure actuated electric switch comprising a sealed hollow capsule having inner and outer ends and a side wall, a pair of electric contacts in the capsule spaced lengthwise thereof, one of the contacts being supported by the outer end of the capsule, said side wall having an annular groove therein reducing the thickness of a portion of the side wall to form a thin band in the wall, and said band being compressible to reduce its width when a predetermined pressure to exerted against said outer end of the capsule, whereby to permit said one contact to engage the other contact, wires electrically connected with said contacts and adapted to be electrically connected with a source of electricity, and an electrically fired cable cutter in series with one of the wires.
 2. A cable cutter comprising a cutting member, an explosive charge for actuating said member, electrical firing means for said charge, a normally open electric circuit containing said firing means, and a normally open water pressure actuated switch in said circuit for closing it when the switch is exposed to a predetermined water pressure.
 3. A cable cutter according to claim 2, including a frame for said cutting member and explosive charge and firing means, said circuit including batteries, and a sealed housing for the batteries rigidly connected to the frame.
 4. A cable cutter according to claim 2, in which said switch includes a sealed hollow capsule having inner and outer ends and a side wall, a pair of electric contacts in the capsule spaced lengthwise thereof, one of the contacts being supported by the outer end of the capsule, said side wall having an annular groove therein reducing the thickness of a portion of the side wall to form a thin band in the wall, and said band being compressible to reduce its width when a predetermined pressure is exerted against said outer end of the capsule, whereby to permit said one contact to engage the other contact.
 5. A cable cutter according to claim 4, including a housing containing said capsule with the outer end of the capsule projecting from the housing, and a cup-like pressure cap engaging Said outer end and slidably mounted on said housing in sealing engagement therewith. 